$CH_3CHO + NH_2OH \to CH_3-CH=N-OH$
Under which condition does the above reaction occur?

$A$ carbonyl compound $P$,which gives a positive iodoform test,undergoes reaction with $MeMgBr$ followed by dehydration to give an olefin $Q$. Ozonolysis of $Q$ leads to a dicarbonyl compound $R$,which undergoes intramolecular aldol reaction to give predominantly $S$.
$P$ $\xrightarrow[\substack{2. H^{+}, H_2 O \\ 3. H_2 SO_4, \Delta}]{1. MeMgBr} Q$ $\xrightarrow[2. Zn, H_2 O]{1. O_3} R$ $\xrightarrow[2. \Delta]{1. OH^{-}} S$
$1.$ The structure of the carbonyl compound $P$ is
$2.$ The structures of the products $Q$ and $R$,respectively,are
$3.$ The structure of the product $S$ is
Give the answer for questions $1, 2$ and $3.$

Which of the following does $NOT$ exhibit haloform reaction?

Which reagent gives an orange-coloured precipitate with acetaldehyde?

The product formed in the following reaction is:
$CHO-CH(OH)-CH_2OH \xrightarrow{2HIO_4} ?$

Write the structures of the products of the following reactions:
$(i)$ $CH_3-CH=CH_2 \xrightarrow{H_2O/H^+}$
$(ii)$ (See image)
$(iii)$ $CH_3-CH_2-CH(CH_3)-CHO \xrightarrow{NaBH_4}$